Field of the Invention
One or more embodiments of the invention relate to an image processing system, a relay server, and a program, and more particularly, to a technology for relaying communication between a server located in the Internet and an image processing apparatus.
Description of the Related Art
Various application servers for SaaS (Software as a Service) applications and the like are located in a cloud in the Internet, and cloud services are provided by the application servers via the Internet these days. A cloud service offers high convenience, as it can be used at anytime from anywhere as long as Internet access is available. In an example of use of a cloud service, the data of documents or the like is stored in an application server, and the data is transferred from the application server to an image processing apparatus located in an intra-company local network, and is printed out.
However, there is a firewall existing between a local network and the Internet. Therefore, when a user issues a job execution instruction to an application server, data is not transferred from the application server in the Internet to an image processing apparatus or the like located in a local network. In view of this, an image processing system shown in FIG. 11 has been suggested so as to realize such data transfer, for example.
The conventional image processing system shown in FIG. 11 includes an application server 110 in the Internet 100, and a connection mediation server 111 cooperating with the application server 110. Meanwhile, in a local network 101 such as an intra-company LAN (Local Area Network), a relay server 120 and image processing apparatuses 130 and 131 are located, for example. There may be only a single image processing apparatus in the local network 101. The relay server 120 is a server that relays communication between the image processing apparatuses 130 and 131 and the application server 110. When activated by a power supply, this relay server 120 establishes a connection 140 to the connection mediation server 111 located in the Internet 100. With this, the connection mediation server 111 becomes able to constantly communicate with the relay server 120 located in the local network 101 over a firewall.
In this image processing system, when the application server 110 transmits a job to the image processing apparatus 130 located in the local network 101, for example, the application server 110 first transmits a communication start request D101 designating the image processing apparatus 130 to the connection mediation server 111. Receiving the communication start request D101, the connection mediation server 111 identifies the relay server 120 that manages the image processing apparatus 130 based on information registered in advance, and transmits a connection request D102 to the relay server 120. This connection request D102 contains address information for connecting to the application server 110, and the like. Receiving the connection request D102 from the connection mediation server 111, the relay server 120 transmits a connection start request D103 to the application server 110 based on the address information and the like contained in the connection request D102. With this, the relay server 120 and the application server 110 are connected, and the application server 110 becomes able to start job transmission to the relay server 120 located in the local network 101. When the job transmission from the application server 110 is completed, the relay server 120 transfers the job received from the application server 110 to the image processing apparatus 130. In this manner, the image processing apparatus 130 becomes able to receive a job transmitted from the application server 110 via the relay server 120, and perform image processing based on the job.
In the above described image processing system, however, all the jobs that are transmitted from a server or the like outside the local network 101 to an image processing apparatus or the like in the local network 101 are relayed by the relay server 120. So as to cause the relay server 120 to achieve a certain processing capacity, there is an upper limit on the number of connections the relay server 120 can establish with a server or the like outside the local network 101, such as the application server 110. If the number of connections between the relay server 120 and the application server 110 is the upper limit, a new connection for transmitting a job cannot be established between the application server 110 and the relay server 120 even when a user issues a job transmission instruction designating the image processing apparatus 130 to the application server 110. In that case, the user has to wait until the relay server 120 becomes able to establish a new connection as the currently-executed job is completed, for example. Therefore, a long period of time might be required for executing a new job. Furthermore, during the period between transmission of a job to the image processing apparatus 130 and completion of execution of the job in the image processing apparatus 130, maintaining a connection between the application server 110 and the relay server 120 even when there is no transmission/reception of data or the like between the two servers is inappropriate in terms of effective use of communication.
In view of this, JP 2009-296473A discloses an image forming apparatus that has a server cooperation function to transmit data to a server and cause the server to process the data. In this image forming apparatus, the connection to the server is temporarily terminated after data is transmitted to the server. When the processing by the server is completed, the server transmits a connection request to the image forming apparatus, so that data can be transmitted from the server to the image forming apparatus. In the above described image processing system, however, there is a firewall existing between a local network and the Internet as described above. Therefore, a connection request cannot be transmitted from the server to the image forming apparatus of JP 2009-296473 A, and the technology disclosed in JP 2009-296473 A cannot be applied to the above described image processing system.